U.S. patent number 11,112,605 [Application Number 16/854,948] was granted by the patent office on 2021-09-07 for diffractive optical elements with asymmetric profiles.
This patent grant is currently assigned to Microsoft Technology Licensing, LLC. The grantee listed for this patent is Microsoft Technology Licensing, LLC. Invention is credited to Lauri Sainiemi, Tuomas Vallius.
United States Patent |
11,112,605 |
Vallius , et al. |
September 7, 2021 |
Diffractive optical elements with asymmetric profiles
Abstract
In an optical display system that includes a waveguide with
multiple diffractive optical elements (DOEs), gratings in one or
more of the DOEs may have an asymmetric profile in which gratings
may be slanted or blazed. Asymmetric gratings in a DOE can provide
increased display uniformity in the optical display system by
reducing the "banding" resulting from optical interference that is
manifested as dark stripes in the display. Banding may be more
pronounced when polymeric materials are used in volume production
of the DOEs to minimize system weight, but which have less optimal
optical properties compared with other materials such as glass. The
asymmetric gratings can further enable the optical system to be
more tolerant to variations--such as variations in thickness,
surface roughness, and grating geometry--that may not be readily
controlled during manufacturing particularly since such variations
are in the submicron range.
Inventors: |
Vallius; Tuomas (Espoo,
FI), Sainiemi; Lauri (Espoo, FI) |
Applicant: |
Name |
City |
State |
Country |
Type |
Microsoft Technology Licensing, LLC |
Redmond |
WA |
US |
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Assignee: |
Microsoft Technology Licensing,
LLC (Redmond, WA)
|
Family
ID: |
56369218 |
Appl.
No.: |
16/854,948 |
Filed: |
April 22, 2020 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20200292814 A1 |
Sep 17, 2020 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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14790379 |
Jul 2, 2015 |
10670862 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B
27/0081 (20130101); G02B 5/1819 (20130101); G02B
27/4205 (20130101); G02B 27/0101 (20130101); G02B
5/1852 (20130101); G02B 27/4272 (20130101); G02B
2027/0112 (20130101); G02B 2027/0178 (20130101); G02B
27/0172 (20130101) |
Current International
Class: |
G02B
27/01 (20060101); G02B 27/42 (20060101); G02B
27/00 (20060101); G02B 5/18 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
"Second Office Action Issued in Chinese Patent Application No.
201680039259.4", dated Apr. 2, 2020, 6 Pages. cited by applicant
.
"Third Office Action Issued in Chinese Patent Application No.
201680039304.6", dated Jul. 9, 2020, 9 Pages. cited by
applicant.
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Primary Examiner: Alexander; William R
Assistant Examiner: Broome; Sharrief I
Attorney, Agent or Firm: Young; Mark K. Mayer &
Williams, PC
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATION
This application is a continuation of U.S. Ser. No. 14/790,379,
filed Jul. 2, 2015, entitled, "DIFFRACTIVE OPTICAL ELEMENTS WITH
ASYMMETRIC PROFILES", the contents of which are hereby incorporated
by reference in its entirety.
Claims
What is claimed:
1. A method of manufacturing an optical display system, comprising:
providing a polymeric substrate of planar optical material;
disposing a first diffractive optical element (DOE) arranged on the
polymeric substrate, the first DOE having an input surface and
configured as an in-coupling grating to receive one or more optical
beams as an input; creating a glass mold having a planar
microstructure comprising features that are asymmetric with respect
to an axis that is orthogonal to the plane of the mold; and using
the mold to form a second DOE on the polymeric substrate which is
configured to receive one or more optical beams from the first DOE
and couples the received one or more optical beams to a third DOE,
and in which the second DOE is configured for pupil expansion of
the received one or more optical beams along a first direction,
wherein at least a portion of the second DOE includes grating
features each having a slant angle to a respective axis orthogonal
to the plane of the polymeric substrate, such that each grating
feature is asymmetric about the axis, and wherein the second DOE is
configured with uniform grating features that are periodic in only
a single direction.
2. The method of claim 1 in which the third DOE is arranged on the
polymeric substrate, the third DOE having an output surface and
configured for pupil expansion of the one or more optical beams
along a second direction, and further configured as an out-coupling
grating to couple, as an output from the output surface, one or
more optical beams with expanded pupil relative to the input.
3. The method of claim 2 in which at least a portion of the third
DOE includes gratings that are configured with a second slant angle
to a direction orthogonal to a plane of the output surface.
4. The method of claim 3 in which at least a portion of the first
DOE includes gratings that are configured with a third slant angle
to a direction orthogonal to a plane of the input surface.
5. The method of claim 1 in which one or more of the asymmetric
grating features comprise one of gratings with slanted sidewalls or
blazed gratings.
6. The method of claim 1 in which microstructure is formed from one
of reactive ion beam etching (RIBE), magnetron reactive ion etching
(MRIE), high density plasma etching (HDP), transformer coupled
plasma etching (TCP), inductively coupled plasma etching (ICP), or
electron cyclotron resonance plasma etching (ECR).
7. A method of producing a molded diffractive optical element (DOE)
in a waveguide-based display system, comprising: providing an
in-coupling DOE that is configured to in-couple input images from
an imager into the waveguide-based display system; providing an
out-coupling DOE that is configured to out-couple output images
from the waveguide-based display system to an eye of a user;
providing a substrate having at least one planar surface; exposing
the substrate to a plasma source to etch a microstructure into the
planar surface in which the microstructure comprises features that
are asymmetric with respect to an axis that is orthogonal to the
planar surface of the substrate; using the etched substrate to mold
a planar DOE from a polymer material in which the molded DOE
includes grating features each having a slant angle to a respective
axis orthogonal to the plane of the DOE; assembling the molded DOE
into the waveguide-based display system with the in-coupling DOE
and the out-coupling DOE to create a light path that sequentially
traverses the in-coupling DOE, the molded DOE, and the output DOE,
wherein at least a portion of the molded DOE includes grating
features each having a slant angle to a respective axis orthogonal
to the plane of the molded DOE, and wherein the molded DOE is
configured with uniform grating features that are periodic in only
a single direction.
8. The method of claim 7 in which the molding comprises one of
cast-and-cure, embossing, compression molding, or injection
molding.
9. The method of claim 7 in which the molded DOE is configured to
provide pupil expansion of the input images from the imager in a
first direction.
10. The method of claim 9 in which the out-coupling DOE is
configured to provide pupil expansion of the input images from the
imager in a second direction.
11. The method of claim 9 in which the imager comprises a
micro-display operating in one of transmission, reflection, or
emission.
12. The method of claim 7 in which at least a portion of the
out-coupling DOE comprises an apodized diffraction grating having
shallow grooves relative to the in-coupling DOE or the molded
DOE.
13. The method of claim 7 in which the display system is configured
as a near eye display system.
14. A method for fabricating a diffractive optical element (DOE),
comprising: providing a reactive ion etching source; affixing a
substrate having at least one planar surface to a moveable holder;
exposing the substrate to the reactive ion etching source to
thereby etch grating features that are asymmetric with respect to
an axis that is orthogonal to the planar surface; controlling the
etching of the substrate to the reactive ion etching source by
motion of the substrate relative to the reactive ion etching
source; using the etched substrate to mold a planar DOE from a
polymer material in which the molded DOE includes grating features
each having a slant angle to a respective axis orthogonal to the
plane of the DOE; and disposing the molded DOE on a waveguide that
includes an in-coupling DOE configured as an in-coupling grating to
receive one or more optical beams as an input, wherein the molded
DOE receives the one or more optical beams from the in-coupling
DOE, and wherein the molded DOE is configured for pupil expansion
along a first direction, and wherein at least a portion of the
molded DOE includes grating features each having a slant angle to a
respective axis orthogonal to the plane of the molded DOE, and
wherein the molded DOE is configured with uniform grating features
that are periodic in only a single direction.
15. The method of claim 14 in which the controlling further
comprises controlling a time of exposure of the substrate to the
reactive ion etching source.
16. The method of claim 14 in which the motion comprises
rotation.
17. The method of claim 14 in which the molded DOE is optically
coupled to an out-coupling DOE disposed on the waveguide, in which
the out-coupling DOE is configured for pupil expansion in a second
direction and for out-coupling the one or more optical beams to an
eye of a user.
18. The method of claim 17 in which the in-coupling DOE, molded
DOE, and out-coupling DOE form an exit pupil expander providing
pupil expansion in two directions.
19. The method of claim 17 in which the exit pupil expander is
incorporated into a head mounted display (HMD) that includes an
imager.
20. The method of claim 19 in which the imager includes one of
light emitting diode, liquid crystal on silicon device, organic
light emitting diode array, or micro-electromechanical system
device.
Description
BACKGROUND
Diffractive optical elements (DOEs) are optical elements with a
periodic structure that are commonly utilized in applications
ranging from bio-technology, material processing, sensing, and
testing to technical optics and optical metrology. By incorporating
DOEs in an optical field of a laser or emissive display, for
example, the light's "shape" can be controlled and changed flexibly
according to application needs.
SUMMARY
In an optical display system that includes a waveguide with
multiple diffractive optical elements (DOEs), gratings in one or
more of the DOEs may have an asymmetric profile in which gratings
are slanted (i.e., walls of the grating are non-orthogonal to the
plane of the waveguide) or blazed. Asymmetric gratings in a DOE can
provide increased display uniformity in the optical display system
by reducing the "banding" resulting from optical interference that
is manifested as dark stripes in the display. Banding may be more
pronounced when polymeric materials are used in volume production
of the DOEs to minimize system weight, but which have less optimal
optical properties compared with other materials such as glass.
Asymmetric gratings can further enable the optical system to be
more tolerant to variations--such as variations in thickness,
surface roughness, and grating geometry--that may not be readily
controlled during manufacturing, particularly since such variations
are in the submicron range.
This Summary is provided to introduce a selection of concepts in a
simplified form that are further described below in the Detailed
Description. This Summary is not intended to identify key features
or essential features of the claimed subject matter, nor is it
intended to be used as an aid in determining the scope of the
claimed subject matter. Furthermore, the claimed subject matter is
not limited to implementations that solve any or all disadvantages
noted in any part of this disclosure.
DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a block diagram of an illustrative near eye display
system which may incorporate the diffractive optical elements
(DOEs) with asymmetric features;
FIG. 2 shows propagation of light in a waveguide by total internal
reflection;
FIG. 3 shows a view of an illustrative exit pupil expander;
FIG. 4 shows a view of the illustrative exit pupil expander in
which the exit pupil is expanded along two directions;
FIG. 5 shows an illustrative arrangement of three DOEs;
FIG. 6 shows a profile of a portion of an illustrative diffraction
grating that has straight gratings;
FIG. 7 shows an asymmetric profile of a portion of an illustrative
diffraction grating that has slanted gratings;
FIGS. 8 and 9 show an illustrative arrangement for DOE
fabrication;
FIGS. 10-12 show various illustrative asymmetric profiles for
slanted gratings;
FIG. 13 shows an illustrative method;
FIG. 14 is a pictorial view of an illustrative example of a virtual
reality or mixed reality head mounted display (HMD) device;
FIG. 15 shows a block diagram of an illustrative example of a
virtual reality or mixed reality HMD device; and
FIG. 16 shows a block diagram of an illustrative electronic device
that incorporates an exit pupil expander.
Like reference numerals indicate like elements in the drawings.
Elements are not drawn to scale unless otherwise indicated.
DETAILED DESCRIPTION
FIG. 1 shows a block diagram of an illustrative near eye display
system 100 which may incorporate diffractive optical elements
(DOEs) with asymmetric profiles. Near eye display systems are
frequently used, for example, in head mounted display (HMD) devices
in industrial, commercial, and consumer applications. Other devices
and systems may also use DOEs with asymmetric profiles, as
described below, and it is emphasized that the near eye display
system 100 is intended to be an example that is used to illustrate
various features and aspects, and the present DOEs are not
necessarily limited to near eye display systems.
System 100 may include an imager 105 that works with an optical
system 110 to deliver images as a virtual display to a user's eye
115. The imager 105 may include, for example, RGB (red, green,
blue) light emitting diodes (LEDs), LCOS (liquid crystal on
silicon) devices, OLED (organic light emitting diode) arrays, MEMS
(micro-electro mechanical system) devices, or any other suitable
displays or micro-displays operating in transmission, reflection,
or emission. The imager 105 may also include mirrors and other
components that enable a virtual display to be composed and provide
one or more input optical beams to the optical system. The optical
system 110 can typically include magnifying optics 120, pupil
forming optics 125, and one or more waveguides 130.
In a near eye display system the imager does not actually shine the
images on a surface such as glass lenses to create the visual
display for the user. This is not feasible because the human eye
cannot focus on something that is that close. Indeed, rather than
create a visible image on a surface, the near eye optical system
100 uses the pupil forming optics 125 to form a pupil and the eye
115 acts as the last element in the optical chain and converts the
light from the pupil into an image on the eye's retina as a virtual
display.
The waveguide 130 facilitates light transmission between the imager
and the eye. One or more waveguides can be utilized in the near eye
display system because they are transparent and because they are
generally small and lightweight (which is desirable in applications
such as HMD devices where size and weight is generally sought to be
minimized for reasons of performance and user comfort). For
example, the waveguide 130 can enable the imager 105 to be located
out of the way, for example, on the side of the head, leaving only
a relatively small, light, and transparent waveguide optical
element in front of the eyes. In one implementation, the waveguide
130 operates using a principle of total internal reflection, as
shown in FIG. 2, so that light can be coupled among the various
optical elements in the system 100.
FIG. 3 shows a view of an illustrative exit pupil expander (EPE)
305. EPE 305 receives an input optical beam from the imager 105
through magnifying optics 120 to produce one or more output optical
beams with expanded exit pupil in one or two dimensions relative to
the exit pupil of the imager (in general, the input may include
more than one optical beam which may be produced by separate
sources). The expanded exit pupil typically facilitates a virtual
display to be sufficiently sized to meet the various design
requirements of a given optical system, such as image resolution,
field of view, and the like, while enabling the imager and
associated components to be relatively light and compact.
The EPE 305 is configured, in this illustrative example, to support
binocular operation for both the left and right eyes (components
which may be utilized for stereoscopic operation such as scanning
mirrors, lenses, filters, beam splitters, MEMS devices, or the like
are not shown in FIG. 3 for sake of clarity in exposition).
Accordingly, the EPE 305 utilizes two out-coupling gratings,
310.sub.L and 310.sub.R that are supported on a waveguide 330 and a
central in-coupling grating 340. The in-coupling and out-coupling
gratings may be configured using multiple DOEs, as described in the
illustrative example below. While the EPE 305 is depicted as having
a planar configuration, other shapes may also be utilized
including, for example, curved or partially spherical shapes, in
which case the gratings disposed thereon are non-co-planar.
As shown in FIG. 4, the EPE 305 may be configured to provide an
expanded exit pupil in two directions (i.e., along each of a first
and second coordinate axis). As shown, the exit pupil is expanded
in both the vertical and horizontal directions. It may be
understood that the terms "direction," "horizontal," and "vertical"
are used primarily to establish relative orientations in the
illustrative examples shown and described herein for ease of
description. These terms may be intuitive for a usage scenario in
which the user of the near eye display device is upright and
forward facing, but less intuitive for other usage scenarios.
Accordingly, the listed terms are not to be construed to limit the
scope of the configurations (and usage scenarios therein) of DOEs
with asymmetric grating features.
FIG. 5 shows an illustrative arrangement of three DOEs that may be
used as part of a waveguide to provide in-coupling and expansion of
the exit pupil in two directions. Each DOE is an optical element
comprising a periodic structure that can modulate various
properties of light in a periodic pattern such as the direction of
optical axis, optical path length, and the like. The first DOE, DOE
1 (indicated by reference numeral 505), is configured to couple the
beam from the imager into the waveguide. The second DOE, DOE 2
(510), expands the exit pupil in a first direction along a first
coordinate axis, and the third DOE, DOE 3 (515), expands the exit
pupil in a second direction along a second coordinate axis and
couples light out of the waveguide. The angle .rho. is a rotation
angle between the periodic lines of DOE 2 and DOE 3 as shown. DOE 1
thus functions as an in-coupling grating and DOE 3 functions as an
out-coupling grating while expanding the pupil in one direction.
DOE 2 may be viewed as an intermediate grating that functions to
couple light between the in-coupling and out-coupling gratings
while performing exit pupil expansion in the other direction. Using
such intermediate grating may eliminate a need for conventional
functionalities for exit pupil expansion in an EPE such as
collimating lenses.
Some near eye display system applications, such as those using HMD
devices for example, can benefit by minimization of weight and
bulk. As a result, the DOEs and waveguides used in an EPE may be
fabricated using lightweight polymers. Such polymeric components
can support design goals for size, weight, and cost, and generally
facilitate manufacturability, particularly in volume production
settings. However, polymeric optical elements generally have lower
optical resolution relative to heavier high quality glass. Such
reduced optical resolution and the waveguide's configuration to be
relatively thin for weight savings and packaging constraints within
a device can result in optical interference which appears as a
phenomena referred to as "banding" in the display. The optical
interference that results in banding arises from light propagating
within the EPE that has several paths to the same location, in
which the optical path lengths differ.
The banding is generally visible in the form of dark stripes which
decrease optical uniformity of the display. Their location on the
display may depend on small nanometer-scale variations in the
optical elements including the DOEs in one or more of thickness,
surface roughness, or grating geometry including grating line
width, angle, fill factor, or the like. Such variation can be
difficult to characterize and manage using tools that are generally
available in manufacturing environments, and particularly for
volume production. Conventional solutions to reduce banding include
using thicker waveguides which can add weight and complicate
package design for devices and systems. Other solutions use pupil
expansion in the EPE in just one direction which can result in a
narrow viewing angle and heightened sensitivity to natural eye
variations among users.
By comparison, when one or more of the DOEs 505, 510, and 515 (FIG.
5) are configured with gratings that have an asymmetric profile,
banding can be reduced even when the DOEs are fabricated from
polymers and the waveguide 130 (FIG. 1) is relatively thin. FIG. 6
shows a profile of straight (i.e., non-slanted) grating features
600 (referred to as grating bars, grating lines, or simply
"gratings"), that are formed in a substrate 605. By comparison,
FIG. 7 shows grating features 700 formed in a substrate 705 that
have an asymmetric profile. That is, the gratings may be slanted
(i.e., non-orthogonal) relative to a plane of the waveguide. In
implementations where the waveguide is non-planar, then the
gratings may be slanted relative to a direction of light
propagation in the waveguide. Asymmetric grating profiles can also
be implemented using blazed gratings, or echelette gratings, in
which grooves are formed to create grating features with asymmetric
triangular or sawtooth profiles.
In FIGS. 6 and 7, the grating period is represented by d, the
grating height by h, bar width by c, and the filling factor by f,
where f=c/d. The slanted gratings in FIG. 7 may be described by
slant angles .alpha..sub.1 and .alpha..sub.2. In one exemplary
embodiment, for a DOE, d=390 nm, c=d/2, h=300 nm,
.alpha..sub.1=.alpha..sub.2=45 degrees, f=0.5, and the refractive
index of the substrate material is approximately 1.71. In other
implementations, ranges of suitable values may include d=250 nm-450
nm, h=200 nm-400 nm, f=0.3-0.0, and .alpha..sub.1=30-50 degrees,
with refractive indices of 1.7 to 1.9. In another exemplary
embodiment, DOE 2 is configured with portions that have asymmetric
profiles, while DOE 1 and DOE 3 are configured with conventional
symmetric profiles using straight gratings.
By slanting the gratings in one or more of the DOEs 505, 510, and
515, banding can be reduced to increase optical uniformity while
enabling manufacturing tolerances for the DOEs to be less strict,
as compared with using the straight grating features shown in FIG.
6 for the same level of uniformity. That is, the slanted gratings
shown in FIG. 7 are more tolerant to manufacturing variations noted
above than the straight gratings shown in FIG. 6, for comparable
levels of optical performance (e.g., optical resolution and optical
uniformity).
FIGS. 8 and 9 show an illustrative arrangement for DOE fabrication
using a substrate holder 805 that rotates a grating substrate 810
about an axis 815 relative to a reactive ion etching plasma source
820. Exposure to the plasma may be used, for example, to adjust the
thickness and orientation of the etching on the grating substrate
at various positions by angling the substrate relative to the
source as shown in FIG. 9 using, for example, a computer-controller
or other suitable control system (not shown). In an illustrative
example, the etching may be performed using a reactive ion beam
etching (RIBE). However, other variations of ion beam etching may
be utilized in various implementations including, for example,
magnetron reactive ion etching (MRIE), high density plasma etching
(HDP), transformer coupled plasma etching (TCP), inductively
coupled plasma etching (ICP), and electron cyclotron resonance
plasma etching (ECR).
By controlling the exposure of the substrate to the plasma, grating
angle and depth can be controlled to create a slanted
microstructure on the substrate. The microstructure may be
replicated for mass production in a lightweight polymer material
using one of cast-and-cure, embossing, compression molding, or
compression injection molding, for example.
Ion beam etching may produce variations from the idealized grating
shown in FIG. 6 in which the gratings have parallel walls. The
profile 1000 in FIG. 10 includes non-parallel sidewalls
(representatively indicated by reference numeral 1005) that are
undercut and the profile 1100 in FIG. 11 includes non-parallel
sidewalls 1105 that are overcut. The change in angle of the
sidewalls is denoted by .beta., as shown in FIG. 10, and a positive
value of .beta. implies undercutting while a negative value of
.beta. implies overcutting. Compensation for the effects of
undercutting and overcutting can be realized in some
implementations by ensuring that a fill factor f.sub.mid in the
center of the feature meets the design value for the grating, as
shown in profile 1200 in FIG. 12. Here, the grating walls
essentially pivot about this center position as .beta. varies.
FIG. 13 is a flowchart 13 of an illustrative method 1300. Unless
specifically stated, the methods or steps shown in the flowchart
and described in the accompanying text are not constrained to a
particular order or sequence. In addition, some of the methods or
steps thereof can occur or be performed concurrently and not all
the methods or steps have to be performed in a given implementation
depending on the requirements of such implementation and some
methods or steps may be optionally utilized.
In step 1305, light is received at an in-coupling DOE. The
in-coupling grating is disposed in an EPE and interfaces with the
downstream intermediate DOE that is disposed in the EPE. In step
1310, the exit pupil of the received light is expanded along a
first coordinate axis in the intermediate DOE. The intermediate DOE
is configured with gratings having an asymmetric profile such as
slanted gratings or blazed gratings. In step 1315, the exit pupil
is expanded in an out-coupling DOE which outputs light with an
expanded exit pupil relative to the received light at the
in-coupling DOE along the first and second coordinate axes in step
1320. The intermediate DOE is configured to interface with a
downstream out-coupling DOE. In some implementations, the
out-coupling DOE may be apodized with shallow gratings that are
configured to be either straight or slanted.
DOEs with asymmetric profiles may be incorporated into a display
system that is utilized in a virtual or mixed reality display
device. Such device may take any suitable form, including but not
limited to near-eye devices such as an HMD device. A see-through
display may be used in some implementations while an opaque (i.e.,
non-see-through) display using a camera-based pass-through or
outward facing sensor, for example, may be used in other
implementations.
FIG. 14 shows one particular illustrative example of a see-through,
mixed reality or virtual reality display system 1400, and FIG. 15
shows a functional block diagram of the system 1400. Display system
1400 comprises one or more lenses 1402 that form a part of a
see-through display subsystem 1404, such that images may be
displayed using lenses 1402 (e.g. using projection onto lenses
1402, one or more waveguide systems incorporated into the lenses
1402, and/or in any other suitable manner). Display system 1400
further comprises one or more outward-facing image sensors 1406
configured to acquire images of a background scene and/or physical
environment being viewed by a user, and may include one or more
microphones 1408 configured to detect sounds, such as voice
commands from a user. Outward-facing image sensors 1406 may include
one or more depth sensors and/or one or more two-dimensional image
sensors. In alternative arrangements, as noted above, a mixed
reality or virtual reality display system, instead of incorporating
a see-through display subsystem, may display mixed reality or
virtual reality images through a viewfinder mode for an
outward-facing image sensor.
The display system 1400 may further include a gaze detection
subsystem 1410 configured for detecting a direction of gaze of each
eye of a user or a direction or location of focus, as described
above. Gaze detection subsystem 1410 may be configured to determine
gaze directions of each of a user's eyes in any suitable manner.
For example, in the illustrative example shown, a gaze detection
subsystem 1410 includes one or more glint sources 1412, such as
infrared light sources, that are configured to cause a glint of
light to reflect from each eyeball of a user, and one or more image
sensors 1414, such as inward-facing sensors, that are configured to
capture an image of each eyeball of the user. Changes in the glints
from the user's eyeballs and/or a location of a user's pupil, as
determined from image data gathered using the image sensor(s) 1414,
may be used to determine a direction of gaze.
In addition, a location at which gaze lines projected from the
user's eyes intersect the external display may be used to determine
an object at which the user is gazing (e.g. a displayed virtual
object and/or real background object). Gaze detection subsystem
1410 may have any suitable number and arrangement of light sources
and image sensors. In some implementations, the gaze detection
subsystem 1410 may be omitted.
The display system 1400 may also include additional sensors. For
example, display system 1400 may comprise a global positioning
system (GPS) subsystem 1416 to allow a location of the display
system 1400 to be determined. This may help to identify real world
objects, such as buildings, etc. that may be located in the user's
adjoining physical environment.
The display system 1400 may further include one or more motion
sensors 1418 (e.g., inertial, multi-axis gyroscopic, or
acceleration sensors) to detect movement and
position/orientation/pose of a user's head when the user is wearing
the system as part of a mixed reality or virtual reality HMD
device. Motion data may be used, potentially along with
eye-tracking glint data and outward-facing image data, for gaze
detection, as well as for image stabilization to help correct for
blur in images from the outward-facing image sensor(s) 1406. The
use of motion data may allow changes in gaze location to be tracked
even if image data from outward-facing image sensor(s) 1406 cannot
be resolved.
In addition, motion sensors 1418, as well as microphone(s) 1408 and
gaze detection subsystem 1410, also may be employed as user input
devices, such that a user may interact with the display system 1400
via gestures of the eye, neck and/or head, as well as via verbal
commands in some cases. It may be understood that sensors
illustrated in FIGS. 14 and 15 and described in the accompanying
text are included for the purpose of example and are not intended
to be limiting in any manner, as any other suitable sensors and/or
combination of sensors may be utilized to meet the needs of a
particular implementation. For example, biometric sensors (e.g.,
for detecting heart and respiration rates, blood pressure, brain
activity, body temperature, etc.) or environmental sensors (e.g.,
for detecting temperature, humidity, elevation, UV (ultraviolet)
light levels, etc.) may be utilized in some implementations.
The display system 1400 can further include a controller 1420
having a logic subsystem 1422 and a data storage subsystem 1424 in
communication with the sensors, gaze detection subsystem 1410,
display subsystem 1404, and/or other components through a
communications subsystem 1426. The communications subsystem 1426
can also facilitate the display system being operated in
conjunction with remotely located resources, such as processing,
storage, power, data, and services. That is, in some
implementations, an HMD device can be operated as part of a system
that can distribute resources and capabilities among different
components and subsystems.
The storage subsystem 1424 may include instructions stored thereon
that are executable by logic subsystem 1422, for example, to
receive and interpret inputs from the sensors, to identify location
and movements of a user, to identify real objects using surface
reconstruction and other techniques, and dim/fade the display based
on distance to objects so as to enable the objects to be seen by
the user, among other tasks.
The display system 1400 is configured with one or more audio
transducers 1428 (e.g., speakers, earphones, etc.) so that audio
can be utilized as part of a mixed reality or virtual reality
experience. A power management subsystem 1430 may include one or
more batteries 1432 and/or protection circuit modules (PCMs) and an
associated charger interface 1434 and/or remote power interface for
supplying power to components in the display system 1400.
It may be appreciated that the display system 1400 is described for
the purpose of example, and thus is not meant to be limiting. It is
to be further understood that the display device may include
additional and/or alternative sensors, cameras, microphones, input
devices, output devices, etc. than those shown without departing
from the scope of the present arrangement. Additionally, the
physical configuration of a display device and its various sensors
and subcomponents may take a variety of different forms without
departing from the scope of the present arrangement.
As shown in FIG. 16, an EPE incorporating DOEs with asymmetric
profiles can be used in a mobile or portable electronic device
1600, such as a mobile phone, smartphone, personal digital
assistant (PDA), communicator, portable Internet appliance,
hand-held computer, digital video or still camera, wearable
computer, computer game device, specialized bring-to-the-eye
product for viewing, or other portable electronic device. As shown,
the portable device 1600 includes a housing 1605 to house a
communication module 1610 for receiving and transmitting
information from and to an external device, or a remote system or
service (not shown).
The portable device 1600 may also include an image processing
module 1615 for handling the received and transmitted information,
and a virtual display system 1620 to support viewing of images. The
virtual display system 1620 can include a micro-display or an
imager 1625 and an optical engine 1630. The image processing module
1615 may be operatively connected to the optical engine 1630 to
provide image data, such as video data, to the imager 1625 to
display an image thereon. An EPE 1635 using one or more DOEs with
asymmetric profiles can be optically linked to an optical engine
1630.
An EPE using one or more DOEs with asymmetric profiles may also be
utilized in non-portable devices, such as gaming devices,
multimedia consoles, personal computers, vending machines, smart
appliances, Internet-connected devices, and home appliances, such
as an oven, microwave oven and other appliances, and other
non-portable devices.
Various exemplary embodiments of the present diffractive optical
elements with asymmetric profiles are now presented by way of
illustration and not as an exhaustive list of all embodiments. An
example includes an optical system, comprising: a substrate of
optical material; a first diffractive optical element (DOE)
disposed on the substrate, the first DOE having an input surface
and configured as an in-coupling grating to receive one or more
optical beams as an input; and a second DOE disposed on the
substrate and configured for pupil expansion of the one or more
optical beams along a first direction, wherein at least a portion
of the second DOE includes gratings that are configured with a
predetermined slant angle to a direction orthogonal to a plane of
the substrate.
In another example, the optical system further includes a third DOE
disposed on the substrate, the third DOE having an output surface
and configured for pupil expansion of the one or more optical beams
along a second direction, and further configured as an out-coupling
grating to couple, as an output from the output surface, one or
more optical beams with expanded pupil relative to the input. In
another example, at least a portion of the third DOE includes
gratings that are configured with a second predetermined slant
angle to a direction orthogonal to a plane of the output surface.
In another example, at least a portion of the first DOE includes
gratings that are configured with a third predetermined slant angle
to a direction orthogonal to a plane of the input surface. In
another example, the one or more optical beams received at the
first DOE emanate as a virtual image produced by a micro-display or
imager.
A further example includes an electronic device, comprising: a data
processing unit; an optical engine operatively connected to the
data processing unit for receiving image data from the data
processing unit; an imager operatively connected to the optical
engine to form images based on the image data and to generate one
or more input optical beams incorporating the images; and an exit
pupil expander, responsive to the one or more input optical beams,
comprising a structure on which multiple diffractive optical
elements (DOEs) are disposed, in which the exit pupil expander is
configured to provide one or more output optical beams, using one
or more of the DOEs, as a near eye virtual display with an expanded
exit pupil, and wherein at least one of the DOEs is configured with
gratings having an asymmetric profile.
In another example, the asymmetric profile comprises one of
gratings with slanted sidewalls or blazed gratings. In another
example, the exit pupil expander provides pupil expansion in two
directions. In another example, the imager includes one of light
emitting diode, liquid crystal on silicon device, organic light
emitting diode array, or micro-electro mechanical system device. In
another example, the imager comprises a micro-display operating in
one of transmission, reflection, or emission. In another example,
the electronic device is implemented in a head mounted display
device or portable electronic device. In another example, each of
the one or more input optical beams is produced by a corresponding
one or more sources. In another example, the structure is curved or
partially spherical. In another example, two or more of the DOEs
are non-co-planar.
A further example includes a method, comprising: receiving light at
an in-coupling diffractive optical element (DOE) disposed in an
exit pupil expander; expanding an exit pupil of the received light
along a first coordinate axis in an intermediate DOE disposed in
the exit pupil expander; expanding the exit pupil along a second
coordinate axis in an out-coupling DOE disposed in the exit pupil
expander; and outputting light with an expanded exit pupil relative
to the received light at the in-coupling DOE along the first and
second coordinate axes using the out-coupling DOE, in which the
intermediate DOE is configured with gratings that have
non-orthogonal orientation relative to a plane of the exit pupil
expander.
In another example, the non-orthogonal orientation comprises a
slant angle of between 30 and 50 degrees from a normal to the
plane. In another example, the in-coupling DOE, the intermediate
DOE, or the out-coupling DOE is formed with a polymer that is
molded from a substrate that is etched using ion beam etching in
which the substrate is rotatable relative to an ion beam source. In
another example, at least a portion of the out-coupling DOE is an
apodized diffraction grating having shallow grooves relative to the
in-coupling DOE or the intermediate DOE. In another example, the
method is performed in a near eye display system. In another
example, the output light provides a virtual display to a user of
the near eye display system.
Although the subject matter has been described in language specific
to structural features and/or methodological acts, it is to be
understood that the subject matter defined in the appended claims
is not necessarily limited to the specific features or acts
described above. Rather, the specific features and acts described
above are disclosed as example forms of implementing the
claims.
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